Obstetrics & Gynaecology/Progestogen LARC

Progestogen LARC (implant / IUS / injectable)

also: Nexplanon · Mirena · Depo-Provera · LARC

Overview

Long-acting reversible contraception — the most effective methods (user-independent). Implant is the single most effective contraceptive.

Mechanism

All deliver a progestogen. Etonogestrel implant and DMPA injection inhibit ovulation + thicken mucus. The LNG-IUS releases levonorgestrel locally → profound endometrial thinning + mucus thickening (ovulation often continues).

Indications

Contraception (most effective)
LNG-IUS: menorrhagia, endometrial protection in HRT

The agents

Etonogestrel implant (Nexplanon)subdermal, 3 yr

most effective

Irregular bleeding common; rapid return of fertility.

LNG-IUS (Mirena/Levosert)intrauterine, 5–8 yr

local action

Also treats heavy menstrual bleeding; lightest systemic effect.

DMPA (Depo-Provera)IM/SC, 12-weekly

depot

Weight gain; delayed fertility (up to 1 yr); reversible ↓BMD.

Adverse effects

Irregular bleedingclassic

DMPA: reduced bone mineral densityserious

Reversible; caution in adolescents and osteoporosis risk; review at 2 years.

DMPA: weight gain + delayed return of fertilitycommon

IUS/IUD insertion: expulsion, perforation, infection riskcommon

Cautions & contraindications

Current breast cancerall

UKMEC 4.

DMPA in major osteoporosis riskall

BMD loss.

IUS: current pelvic infection / distorted cavity / unexplained bleedingall

Interactions

Implant/DMPA efficacy reduced by enzyme inducers (IUS unaffected — local action)

Monitoring & kinetics

DMPA: review BMD risk at 2 years,Bleeding pattern

Implant 3 yr; IUS 5–8 yr; DMPA every 12 weeks.

Source: FSRH — LARC · BNF — Contraceptives